1. Technical Field
The present disclosure relates to a method of regulating light wavelength, to and more particularly, to a method of regulating light wavelength for a projection device.
2. Description of Related Art
In a laser projector, the optical path design of a light source module is generally designed by transmitting a single-color light through a phosphor wheel (PW) so as to excite red, yellow, or green phosphors as a light source for display. And then, the light sequentially passes through a relay, a light modulator and projection lens to emit a specific color light as a light source.
FIG. 1 is a schematic view of a light source module 100 of a general 445-nm laser projector. In FIG. 1, a 445-nm blue light source 110 first emits a blue light 111, so that the blue light 111 enters a phosphor wheel 120 and excites a phosphor layer 121, to generate another color light 122 with a longer wavelength. The residual blue light 111 may enter the projector through another optical path as a blue light source.
However, the general 445-nm laser light source presents purplish (the left side of FIG. 2A), and has an obvious color difference from the standard blue light source provided in Rec. 709 (the right side of FIG. 2A), as shown in FIG. 2A. The CIE (International Commission on Illumination) coordinate (x, y) of the general 445-nm laser light source is (0.13, 0.03) (point 210 in FIG. 2B), which is different from the CIE coordinate (0.15, 0.06) (point 220 in FIG. 2B) of Rec. 709, as shown in FIG. 2B. Such phenomenon may seriously impact the display gamut of a projector, and generate a serious color shift in blue color.
Currently, 445-nm blue has been used to excite a green phosphor to to generate a cyan light. And, the cyan light in a specific range of wavelength is screened by a filter, and mixed with 445-nm blue light to adjust the blue color. However, such light-mixing method needs an additional cyan-light filter and the change in the optical pathway of the original light source, such that extra components and product cost are involved. Further, the aforementioned method still cannot efficiently adjust the blue light source to conform the CIE coordinate of Rec. 709.
Therefore, there is a need for an improved method of regulating light wavelength for a projection device, so as to solve the color shift of the conventional blue light source met in the art.